Considering a Subwoofer build and would appreciate your thoughts. - Page 2 - AVS Forum
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post #31 of 51 Old 08-15-2013, 10:40 AM
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sorry, i put this in the wrong place.

it belonged here: http://www.avsforum.com/t/1486044/help-with-si-18-ht-4-sonotube-build#post_23633340

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post #32 of 51 Old 08-15-2013, 10:57 AM
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^ I'm still perfectly happy, but I look at stuff like that sometimes and think I should have just built two giant 18" ported cabs. Simply ridiculous for 99/100 users in 99/100 rooms.


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post #33 of 51 Old 08-16-2013, 05:58 AM - Thread Starter
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Thanks for your help everyone. After poking around the net, I think I will attempt to build a down firing version of this one. From what I gather, a 15" sealed, down firing sub with the amp I have will be the way to go. 3 cubic feet seems to be the target?


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post #34 of 51 Old 08-16-2013, 06:20 AM
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The MFW-15 is very similar to the Dayton DVC, and I believe that it can be used as a direct replacement for the MFW.

How does that JBL GTO stack up against the Dayton DVC?
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post #35 of 51 Old 08-16-2013, 07:02 AM
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Quote:
Originally Posted by mr.pope View Post

Thanks for your help everyone. After poking around the net, I think I will attempt to build a down firing version of this one. From what I gather, a 15" sealed, down firing sub with the amp I have will be the way to go. 3 cubic feet seems to be the target?



Sealed if you can defeat the high pass on the amp and you don't use the other 12" Klipsch sub.

You really should build a 20-25hz ported box if you are using the Klipsch amp and other sub. 5-7cu ft would be good for the 385 DVC.
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post #36 of 51 Old 08-16-2013, 07:21 AM - Thread Starter
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Good to know. I'd like to build it a similar size to an end table I have. When I fugure out the dimensions, I may need a little help with the port size.
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post #37 of 51 Old 08-29-2013, 05:49 AM - Thread Starter
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Ok, I'm not sure if I'm using this right, or even thinking about it right. But my plans to replicate an existing corner table gives me a volume of 5.55 cu ft. I'm not sure what this is telling me. From the graphs, the ported Dayton gives the best curve, but the JVC is a bit more powerful?


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post #38 of 51 Old 08-29-2013, 07:59 AM
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Quote:
Originally Posted by mr.pope View Post

Ok, I'm not sure if I'm using this right, or even thinking about it right. But my plans to replicate an existing corner table gives me a volume of 5.55 cu ft. I'm not sure what this is telling me. From the graphs, the ported Dayton gives the best curve, but the JVC is a bit more powerful?



The GTO has slightly more sensitivity in the upper range and less in the lower. This makes sense since it's a car sub.

You don't really get the full picture with just the SPL graph. That is small signal frequency response. You need to look at max spl to model how the perform with large signal.
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post #39 of 51 Old 08-29-2013, 08:29 AM - Thread Starter
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How do I do that?
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post #40 of 51 Old 08-29-2013, 09:59 AM
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I'm not familiar with that version of winisd. Pro alpha has a dropdown.
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post #41 of 51 Old 08-29-2013, 11:00 AM - Thread Starter
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Yeah, there is a drop down, but when I switch it over, the graph is out of range and the changes I make to the axis ranges on the graph don't take, so I can't see what is going on.
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post #42 of 51 Old 08-29-2013, 11:54 AM
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You just set your end spl to something high like 120db.
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post #43 of 51 Old 08-30-2013, 11:53 AM - Thread Starter
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Here is my first set of plans. Please criticize it.

Using the klipsch amp and the Dayton DVC385, the box design I came up with:



Volume 5.65 to 5.75 (depending upon the bracing) I've messed with the numbers to get a range, but haven't drawn it yet.
Ported with a 4" flared port, tuned to 20Hz



Should I change anything? Is there anything that I should be concerned about or push a dimension one way or another for better performance?

thanks in advance.
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post #44 of 51 Old 08-30-2013, 12:11 PM
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The port is a little small and I would point it out the side if it doesn't ruin your aesthetic too much.

Link calculates minimum port dia to 6.33". You could get away with 6" and a small flare like 1/2" round-over. That's going to make your port about 30" long so you will need an elbow.
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post #45 of 51 Old 08-30-2013, 12:25 PM - Thread Starter
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thanks.

I calculated the port length with winisd and then double checked it with you link. I get 4" minimum with a length of 12". Do you think that will be too loud? And, Technically, dose it mater where the port is?
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post #46 of 51 Old 09-03-2013, 07:19 AM
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A 4" port gives you a port air velocity of 46m/s at 16hz with 350w. That port is too small.

You need a 6" port, which lowers the air velocity to 20m/s at 16hz, to avoid port noise. To keep the same 20hz tune, the 6" diameter port will need to be 30" long.

No, it doesn't make any difference where you put the port, except that it should be about 1 x diameter away from any boundary. This is harder to do if the port is on the bottom of the box because you then need to make the legs 6" tall to keep the port away from the floor.
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post #47 of 51 Old 09-03-2013, 05:06 PM
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Moving the port away from the floor does change the response though. The modeling for near boaundary conditions can be favorable depending on desired frequency range. For a subwoofer where the wavelength is long you might want the gain. The dips in frequency response are an issue as you climb into the mid-bass region which should not be an issue with a sub-woofer.
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post #48 of 51 Old 09-03-2013, 06:35 PM
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Quote:
Originally Posted by colofan View Post

Moving the port away from the floor does change the response though.
Only if it approaches 1/4 wavelength within the port pass band. If that's centered at 20Hz 1/4 wavelength is 14 feet, and still 7 feet an octave higher, so seldom is port location an issue. The exception is when the air space between the port and the boundary is configured specifically as an actual extension of the port, in which case varying the distance changes the box tuning.

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post #49 of 51 Old 09-11-2013, 10:51 AM - Thread Starter
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Thanks for the input guys, I've been off the web for awhile fishing. I've been tweaking it a bit to accommodate the 6" port. I decided to make it a little bigger in order to better fit the 6" port. Let me know if you think of the changes.

Down-firing Dayton sub
7.82 cubic ft, tuned to 20Hz
Klipsch amp
6", 20.91" long flared port






Sorry, the port kind of looks like a driver.
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post #50 of 51 Old 09-11-2013, 11:46 AM
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Quote:
Originally Posted by LTD02 View Post

"Sealed subs give a tight punch."

not sure where that comes from. ported and horns can give tight punch too.

http://www.avsforum.com/t/1387178/archaeas-kansas-city-blind-subwoofer-shootout-2012

Yes, and I said they can. But even the members of the listening panel you linked to preferred the sealed subs. What I said was some ported subs provide tight, defined bass but all sealed subs do. Where it comes from is common knowledge and my own experience. I'm not against ported subs I just think the sound quality of sealed subs is worth the compromises - at least for me. I said that too. I didn't suggest they were for everybody.
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post #51 of 51 Old 09-11-2013, 12:06 PM
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"Yes, and I said they can. But even the members of the listening panel you linked to preferred the sealed subs."

how could they prefer the sealed subs when they couldn't tell which ones were sealed, ported, or horns?



"What I said was some ported subs provide tight, defined bass but all sealed subs do. Where it comes from is common knowledge..."

i'm not aware of the common knowledge that you are talking about.

just not sure what you are say'n...

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